Heat pump with thermal energy transfer unit and method

ABSTRACT

A thermal energy transfer unit is used in conjunction with a conventional Freon based heat pump system. One or several thermal energy transfer units are operatively interconnected to one or several Freon based heat pump systems and share a common energy storage tank. Each thermal energy transfer unit converts energy from a compressor and condensing coil of the conventional heat pump system and stores it in the common energy storage tank when electricity is in low demand. Each thermal energy transfer unit retrieves stored energy from the common storage tank and provides air conditioning without the use of the compressor when electricity is in high demand. Each thermal energy transfer unit can be disabled to allow the heat pump units to perform as if they and the energy storage tank were not connected. One or all of the units can be disabled without affecting the performance or purpose of the others.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a heating and cooling unitsof the type employing a heat pump for maintaining an environmentenclosed by a structure at a selectively desired comfort range.

2. Description of the Prior Art

Air-conditioning can be defined as the control of temperature, humidity,purity, and motion of air in an enclosed space, independent of outsideconditions. There are a number of technologies which exist in the priorart to control the environmental conditions of an enclosed space,ranging from simple evaporative systems which provide cooling in anenclosed space by evaporation of water from a fixed media, to moreadvanced techniques that employ more sophisticated air-conditioningtechnology.

In traditional air conditioning systems employed for many years incommerce, a refrigerant, normally consisting of a Freon compound (carboncompounds containing fluorine and chlorine or bromine), in a volatileliquid form, is passed through a set of evaporator coils located in thespace to be cooled. The refrigerant evaporates and, in the process,absorbs the heat contained in the air in the enclosed space. When thecooled air reaches its saturation point, its moisture content condenseson fins placed over the coils. The water runs down the fins and drains.The cooled and dehumidified air is returned into the room by means of ablower. During this process, the vaporized refrigerant passes into acompressor where it is pressurized and forced through condenser coils,which are in contact with the outside air. Under these conditions, therefrigerant condenses back into a liquid form and gives off the heat itabsorbed inside the enclosed space. This heated air is expelled to theoutside, and the liquid recirculates to the evaporator coils to continuethe cooling process.

In some units, the two sets of coils can reverse functions so that inwinter, the inside coils condense the refrigerant and heat rather thancool the room or enclosed space. These units are referred to as a “heatpump” in the discussion which follows.

Both the above described traditional mechanical refrigeration airconditioning systems and heat pumps require work in the form of theenergy required to operate the associated mechanical compressor in thesystems. Although air-conditioning units of these types are widely usedin the industry, they are typically relatively expensive to operate asthey use relatively large amounts of electrical power

As previously mentioned, another system of cooling air in an enclosedspace is simply by means of passing air through water for cooling theair by means of evaporation. These systems are known in the industry as“evaporative coolers.” Although evaporative coolers are less expensiveto operate, they do not recirculate the air in the same manner as aFreon based air conditioner, and are not as effective in operation whenthe humidity in the environment rises. Furthermore, over time,evaporative coolers tend to use large amounts of water, and provide abuildup of humidity within the structure which can lead to mildewbuildup and other problems.

Alternate systems of cooling the interior of a structure include the useof chilled water. Water may be cooled by refrigerant at a centrallocation and run through coils at other places. Water may be sprayedover selected media which then has air blown through it. Although largecommercial systems of this type are currently used in industry, they uselarge amounts of water, which may not be practical for dryer regions ofthe country where water is less abundant and may not be economicallyfeasible for smaller installations.

In recent years, the utility electrical industry has incorporatedreduced electrical rates in off-peak hours when demand is low. As aresult, the electrical consumer has found it advantageous to purchaseand “store” the energy needed for air conditioning in the off-peak hoursand use it during peak hours. This typically involves the use of aninsulated tank of some sort. There are many methods of storing andretrieving thermal energy from an insulated tank. All require aninsulated tank that contains a substance in which the thermal energy isstored.

One method utilizes a liquid that simply stores the thermal energy byreducing the temperature of the liquid. For example, if this liquid iswater, one pound of water stores approximately one BTU per degree ofFahrenheit temperature reduction. The energy is stored by removing heatfrom the liquid by various methods. The energy is recovered bycirculating the cooled liquid into a heat exchanger during peak hourswhere it absorbs heat because of the low temperature of the liquid.

Another method of thermal energy storage involves the freezing of theliquid inside the insulated tank to its solid state by various methods.The heat stored per pound of liquid is much greater because of thechange of state of the liquid to solid. If water is the liquid, onepound of water stores approximately 144 BTU's per degree of Fahrenheittemperature reduction, the phenomenon being referred to as the latentheat. The energy is recovered from storage by circulating a substance(sometimes the same melted liquid) through or around the cold solidtransferring heat to the solid until it is all melted back to its liquidstate.

Another method of thermal energy storage is a combination of the twopreviously described methods. Thermal energy is stored by transferringheat out of a liquid until a portion of the liquid solidifies to a solidstate resulting in a slurry of solid particles floating in a liquid.Thermal energy is retrieved by circulating the liquid of the slurry tothe area to be cooled where heat is added to the cool liquid. The heatis rejected to the particles of solid floating in the slurry.

Because of problems involved in creating the above slurry and thusstoring thermal energy, another method has evolved which uses sealedspherical balls containing a liquid that changes to its solid state tostore thermal energy. These balls are contained in a liquid that freezesat a much lower temperature than the liquid contained in the balls.Energy is stored by removing heat from the low temperature liquid untilthe liquid inside the balls changes to the solid state. Energy isrecovered by circulating the low temperature liquid to the area to whereheat is added and then rejected to the melting of the liquid inside theballs. U.S. Pat. No. 4,768,579, issued to Patry, is an example of thismethod.

All of these methods have advantages and disadvantages, depending uponthe particular end applications, methods of storing and retrieving heat,and commercial considerations of tank size, tank location, etc. All ofthese methods retrieve the stored energy by circulating a liquid totransfer the heat removed from the air conditioned area to the tankcontaining the material in which thermal energy is stored.

Past efforts for this method of conversion and storage of thermal energyhave generally used a conventional condensing unit. Thus, past effortsfor this method have typically used a coil submerged in liquid containedin the insulated tank for the thermal energy conversion and storage.These submerged coils had Freon flow through them to freeze the liquidto its solid state for energy storage. The same coil was used for storedenergy recovery by flowing Freon through the coil where it condensed toits liquid state, thus adding heat to the frozen liquid in the tank.There were various deficiencies with this type of system, however. Forexample, these systems generally require the water that is frozen andthe coil inside it to be located near the Freon compressor because ofpressure losses in the Freon tubing between the compressor and the coil,compressor lubricating oil loss and entrapment in long runs of Freontubing between the coil and compressor. The additional cost andinconvenience of the copper tubing connecting the coil and thecompressor must be taken into consideration when the two are locatedapart at a relatively great distance.

Additionally, even though the above described “heat pump” technologyusing the reversible flow of a compressible refrigerant has beenavailable for many years, the existing heat pump systems, particularlythose intended for smaller system installations, have not takenadvantage of the technique of storing thermal energy in a tank and theuse of chilled water as an auxiliary energy source for use during peakenergy consumption hours of the day. There exists, therefore, a need foran improved apparatus and method for allowing a conventional Freon basedheat pump system to store and then retrieve thermal energy in the tankusing any of the above cited methods of thermal energy storage,depending upon the particular situation at hand.

SUMMARY OF THE INVENTION

It is therefore one object of the invention to provide a unique thermalenergy transfer unit which can be used with a thermal energy storagetank and which can be adapted to a conventional heat pump installation.

It is another object to provide such a system which does not necessarilyrequire the thermal energy storage tank to be located in close proximityto the heat pump.

It is another objective of this invention to provide a thermal energytransfer unit and storage system for a heat pump which can be easilyretrofitted to an existing heat pump system without requiring changingthe plumbing located inside the structure to be cooled or heated.

It is another objective of this invention to provide a thermal energystorage tank and apparatus which allows the transfer of thermal energyfrom the existing condensing unit of the heat pump to the remote thermalenergy storage tank during off-peak hours, while allowing recovery ofthis energy from the storage tank during peak hours.

In accordance with the teachings of the present invention, there isprovided an improved method for heating and cooling a structure using aconventional Freon based heat pump system. In the system of theinvention, a first refrigerant based heat exchanger located within thestructure is provided which is capable of acting as either an evaporatoror a condenser and adapted to absorb thermal energy from a structure ina cooling mode and supply thermal energy to the structure in a heatingmode. A second refrigerant based heat exchanger located outside thestructure is provided which is also capable of acting as either anevaporator or a condenser and adapted to absorb thermal energy fromambient atmosphere in a one mode and being adapted to transfer thermalenergy to ambient atmosphere in a different mode. A refrigerantdistribution loop containing a compressible Freon based refrigerantconnects the first and second heat exchangers in fluid flowcommunication. A refrigerant compressor is provided to cycle therefrigerant through the refrigerant distribution loop and the first andsecond heat exchangers. The system also includes a reversing valve forconverting the system from one of the aforesaid heating and coolingmodes to the other of the modes by reversing the flow of Freon basedrefrigerant in the refrigerant flow loop.

The improvements provided by the method of the invention include theprovision of a thermal energy transfer unit in heat exchangerelationship to the refrigerant distribution loop for applying energyconversion and storage to the Freon based heat pump system associatedwith the structure as the flow of Freon is reversed in the refrigerantflow loop during the cycling of the heating and cooling modes ofoperation of the system. The preferred thermal energy transfer unitincludes a non-freezing liquid thermal storage media located in athermal storage tank. The thermal energy transfer unit is utilized totransfer heat from the thermal storage media in the thermal storage tankto the first heat exchanger of the Freon based heat pump system. Heatcan be transferred from inside air within the structure to the thermalstorage media in the thermal storage tank without the compressor of theconventional heat pump system operating. Thereafter, the first heatexchanger can be allowed to transfer heat from the inside air of thestructure to outside air in the same manner that such heat transfer wasaccomplished before the thermal energy transfer unit and thermal storagetank were added to the existing Freon based heat pump system.

The second refrigerant based heat exchanger in the heat pump systemincludes an outside coil which acts as the evaporator in the system whenthe system is in the heating mode for heating the structure, and whereinthe outside coil tends to ice up during the heating mode operation,normally requiring a thawing step between the cooling and heating modesof the system. In the method of the invention, the outside coil isthawed without the use of electric heating elements by reversing theflow of refrigerant in the refrigerant loop, thereby causing the outsidecoil to act as a condenser, the heat transfer between the refrigerantloop in the heat pump system and the storage media in the thermalstorage tank being used to cool the thermal storage media and make icein the thermal storage tank

In the improved system of the invention, the thermal storage tank isconnected at an inlet and at an outlet to a fluid flow line. A fluidpump is provided for pumping non-freezing liquid to and from the storagetank to the thermal energy transfer unit. The preferred system includesan external heating element which is in heat exchange contact with theflow line to heat the non-freezing liquid being circulated to thestorage tank during the thawing step of the heat pump system.

The thermal energy transfer unit of the invention allows normal airconditioning to be performed by the operation of the heat pumpcompressor and condensing coil as if the thermal energy transfer unitwere not present, in which case heat is neither being added to norextracted from the non freezing liquid in the storage tank and theliquid pump in the fluid flow line is not running.

The thermal energy storage tank which is used in the method of theinvention can use any of a variety of media for storing energy. Forexample, the media can be selected from among: chilling a non-freezingliquid such as a water/glycol solution; using an ice on pipe storagetank; using an ice ball storage tank; and using an ice slurry method forstoring thermal energy.

The preferred thermal energy transfer unit includes at least oneauxiliary heat exchanger for transferring heat from a conventional heatpump system having a mechanical compressor in a closed looprefrigeration circuit to a non-freezing liquid medium that, in turn,transfers that heat to or from at least one thermal storage tank. A pumpis provided for circulating the non-freezing liquid medium. A valvecontrol circuit controls the flow of the non-freezing liquid medium tothe conventional heat pump system to enable the transfer of heat to thethermal storage tank without the mechanical compressor of the heat pumpsystem running. The valve control circuit includes a series of valveswhich are used to start, stop and regulate the flow of heat from theconventional heat pump system to or from the thermal storage tank, thevalve control circuit also functioning to allow heat to be transferredby the heat pump system as if the thermal energy transfer unit andthermal storage tank were not present in the system. The thermal energytransfer operates to duplicate the operation of a conventional airconditioner condensing unit while operating in the cooling mode, butwithout the conventional air conditioner condensing unit operating. Aplurality of thermal energy transfer units can be used in associationwith a plurality of heat pump systems to transfer heat to or from one ormore shared thermal energy storage tanks.

These and other aspects of the invention will be better appreciated andunderstood when considered in conjunction with the following descriptionand the accompanying drawings. It should be understood, however, thatthe following descriptions, while indicating preferred embodiments andnumerous specific details thereof, are given by way of illustration andnot of limitation. Many changes and modifications may be made within thescope of the embodiments herein without departing from the spiritthereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic representation of a conventional Freonbased heat pump system shown operating in the air conditioning mode.

FIG. 2 is a simplified schematic view, similar to FIG. 1, but showingthe conventional heat pump system operating in the heating mode.

FIG. 3 is a simplified schematic diagram of the heat pump system of FIG.1 but with Applicant's improved thermal energy transfer unit and thermalenergy storage tank and with the system operating in the normal airconditioning mode.

FIG. 4 is a view similar to FIG. 3, but with the system operating in thenormal heating mode.

FIG. 5 is a view of the improved system of the invention in which noheating or cooling is occurring within the structure, the thermal energystorage media being cooled in the thermal energy storage tank.

FIG. 6 is a schematic representation of the operation of the system ofthe invention where the compressor of the conventional heat pump is notrunning and air conditioning of the structure is being achieved bycirculating cold, non-freezing liquid from the thermal energy storagetank to an auxiliary heat exchanger which, in turn, is in a heatexchange relationship with the Freon being circulated in the heat pumpsystem.

FIG. 7 is a simplified schematic of the operation of the conventionalheat pump system in the thaw out mode where the external heat exchangercoil is being defrosted.

FIG. 8 is a schematic representation of another mode of operation ofApplicant's system in which the external heat exchanger coil of the heatpump is being defrosted by cooling the media in the thermal energystorage tank.

FIG. 9 is a view similar to FIG. 8, but shows the addition of a heatingcoil on the fluid flow line in order to raise the temperature of thenon-freezing liquid while the system simultaneously defrosts theexternal heat exchanger coil of the conventional heat pump.

FIG. 10A is a table illustrating the component status of each of theoperative components of the systems described in the drawings.

FIG. 10B is a continuation of the table of FIG. 10A.

DETAILED DESCRIPTION OF THE INVENTION

The nature of the present invention and the various features andadvantageous details thereof are explained more fully with reference tothe non-limiting examples that are illustrated in the accompanyingdrawings and detailed in the following description. Descriptions ofwell-known components and processes and manufacturing techniques areomitted so as to not unnecessarily obscure the more important featuresof the invention described herein. The examples used are intended merelyto facilitate an understanding of ways in which the invention may bepracticed and to further enable those of skill in the art to practicethe various embodiments of the invention. Accordingly, the examplesshould not be construed as limiting the scope of the claimed invention.

FIG. 1 is a simplified schematic representation of a conventional Freonbased heat pump system which is used to air condition or heat astructure such as the building (14 in FIG. 1). In FIG. 1, the system isshown in the normal air conditioning mode. In the discussion whichfollows, the term “Freon air conditioning” is intended to describe anyconventional mechanical compression refrigeration or air conditioningsystem using a compressible refrigerant and an expansion device in aclosed circuit to achieve a cooling effect by the liquid/vapor phasechange of the compressible refrigerant. The term “Freon” is intended tobe descriptive of that general class of refrigerants containingdifferent chlorofluorocarbons, or CFCs, which are widely used incommerce and industry. The CFCs are a group of aliphatic organiccompounds containing the elements carbon and fluorine, and, in manycases, other halogens (especially chlorine) and hydrogen. Freons arecolorless, odorless, nonflammable, noncorrosive gases or liquids. Thus,a number of compressible refrigerants of the same general class will beknown to those skilled in the relevant industries and that the term“Freon” is used in the discussion which follows merely as a shorthandfor describing this general class of refrigerants.

The building 14 has an inside heat exchange coil 9, an inside expansiondevice 12, a check valve 13 and a motorized air mover 10 located insidethe building. The coil 9, expansion valve 12 and check valve 13 are alllocated in a refrigerant flow loop 37 in which Freon refrigerant isbeing circulated. In the normal air conditioning mode, the air 11 insidethe building 14 is moved past the inside coil 9 when the motorized airmover 10 is running. The components shown in FIG. 1 which are locatedinside the building structure 14 are referred to in the discussion whichfollows as a “first refrigerant based heat exchanger” or “inside heatexchanger” capable of acting as either an evaporator or a condenser andadapted to absorb thermal energy from a structure in a cooling mode andsupply thermal energy to the structure in a heating mode.

The system of FIG. 1 also has what will be referred to herein as a“second refrigerant based heat exchanger” or “outside heat exchanger”which is also capable of acting as either an evaporator or a condenserand adapted to absorb thermal energy from ambient atmosphere in a onemode and being adapted to transfer thermal energy to ambient atmospherein a different mode. The second heat exchanger includes a refrigerantcompressor 1, an outside coil 4, an outside air mover 5, an expansionvalve 6 and a check valve 7. The components other than the air mover areall in fluid communication in the refrigerant flow loop 37 containingthe compressible Freon based refrigerant. Outside air 8 is moved pastthe outside coil 4 when the motorized air handler 5 is on and running. Areversing valve 2, located outside the building structure in associationwith the second heat exchanger is provided for reversing the flow ofrefrigerant in the refrigerant flow loop, as will be described ingreater detail.

In the air conditioning mode, the first and second heat exchangersoperate to transfer heat from the inside air within the structure to theoutside air. The compressor 1 is the prime mover and comes on when theinside air temperature rises. The compressor 1 pulls the Freon from theinside (evaporator) coil 9 through the refrigerant flow loop 37, throughthe reversing valve 2 and loop leg 39, to the compressor, where it is ina low pressure and vapor state. The compressor 1 compresses the vapor,causing the vapor to leave the compressor through the loop leg 41 at ahigh pressure and an elevated temperature in the vapor state. Thecompressed Freon then flows to the outside heat exchanger coil 4 throughthe connecting conduit. In this mode of operation, the outside coil 4acts as a condensing coil. As outside air moves across the outside(condensing) coil 4, the elevated temperature of the Freon vapor in thecondensing coil 4 causes heat to transfer to the outside air. In thismanner all of the heat absorbed from the inside air and all theadditional heat added to the Freon in the form of work during thecompression cycle is rejected to the outside air. As this heat isrejected to the outside air, the Freon within the outside (condensing)coil 4 condenses to its liquid state at this elevated pressure. As aresult, the Freon leaves the condensing coil 4 as a high pressure liquidthrough the refrigerant flow line and travels past check valve 7 throughthe loop leg 43 inside the structure 14 to be cooled and to theexpansion device, in this case inside expansion valve 12. The expansionvalve 12 holds back pressure on the liquid.

There are several different types of expansion devices that can be used,all of which cause the pressure entering the device to be much higherthan the discharge. The Freon leaves the expansion device 12 at a lowpressure through the loop leg 45 of the refrigerant flow loop andtravels to the inside coil 9, which in this mode of operation acts as anevaporator coil. Inside the evaporator coil 9, the Freon starts tovaporize because of its low pressure and added heat. As it vaporizes,the temperature of the Freon decreases until it is lower than the insideair moving past the coil 9. Because of this low temperature, heat istransferred from the inside air to the Freon as it vaporizes. The inside(evaporator) coil 9 and the motorized air mover 10 are sized such thatall the Freon is vaporized in the evaporator coil 9. The Freon leavesthe evaporator coil 9 through the loop leg 45 of the refrigerant flowloop and returns to the compressor 1 after passing through the reversingvalve 2, where it again repeats the cycle. Typically the temperature ofthe inside air is monitored. When the inside air temperature reaches adesired set point, the compressor 1 and motorized air movers 5 and 10are turned off. When the inside air temperature rises they are turnedon.

FIG. 2 is a schematic diagram of the previously described conventionalheat pump system but showing the system in the heating mode, rather thanin the previously described air-conditioning mode. In the operationbeing illustrated in FIG. 2, the flow of the compressible refrigerant inthe refrigerant flow loop is reversed by the action of the reversingvalve 2. The outside and inside coils, 4 and 9 respectively, thenoperate in exactly the opposite manner to that previously described sothat the air mover 10 transfers heat to the air inside the structure. Inother words, the reversing valve 2 redirects the discharge from thecompressor 1 so that high pressure vapor passes through the inside coil9. Freon leaves the coil 9 as a high pressure liquid. The Freon thengoes through the check valve 13 which is parallel to the closedexpansion valve 12 and is directed to the expansion valve 6 located onthe outside of the building structure. It passes in as a high pressureliquid, but out as a cold, low pressure vapor. The refrigerant thenpasses through the outside coil 4, whereby the outside air is, ineffect, being cooled.

The operation of this type of conventional heat pump system will befamiliar to those skilled in the HVAC industries. One advantage of sucha system is that practically all of the work going into the compressor 1ends up as heat energy in the inside coil 9 located inside the buildingstructure.

FIG. 3 is a simplified schematic illustration showing the previouslydescribed heat pump system to which has been added a thermal energytransfer unit (TETU) 100 and an associated thermal energy storage tank32. The thermal energy transfer unit (TETU) 100 consists of a means totransfer heat to or from a non-freezable liquid which is beingcirculated to and from the thermal energy storage tank 32. The othercomponents of the system include an auxiliary heat exchanger 20, anexpansion device 22, a means of pumping liquid Freon 18, a means ofpumping the non-freezable liquid 19 and the associated flow valves andcheck valves needed to control the Freon flow.

It is important to note that the term “non-freezing liquid” is intendedin the description which follows to describe a different thermal mediafrom the Freon type refrigerant being circulated in the conventionalheat pump system. The term “non-freezing liquid” is used herein todescribe a generally non-compressible liquid, such as a water/glycolsolution which is pumped by means of the positive displacement liquidpump 19 in FIG. 3. The non-freezing liquid is in heat exchangerelationship with the Freon flow loop 37 by means of the auxiliary heatexchanger coil 20, but the non-freezing liquid does not undergo a phasechange from vapor to liquid, as is occurring in the primary Freon basedheat pump circulation loop.

The thermal energy storage tank may contain any of a number of knownthermal energy storage media materials as described, for example, inApplicant's issued U.S. Pat. No. 7,152,413. These include, for example,lowering the temperature of a liquid located within an insulated tank;by chilling a non-freezing liquid such as a water/glycol solution; usingan ice on pipe storage tank; using an ice ball storage tank; and usingan ice slurry method for storing thermal energy.

The primary purpose of Applicant's TETU is to provide a method for:

-   -   1. transferring heat from a thermal storage media in the thermal        storage tank 32 to the heat pump system where it is rejected to        outside air;    -   2. transfer heat from the inside air of the building structure        14 to the thermal storage media in the thermal storage tank 32        without the compressor of the heat pump system operating; and to    -   3. allow the inside and outside heat exchangers of the heat pump        system to transfer heat from the inside air of the building        structure to outside air in the same way which has been        described in FIG. 1 before the TETU 100 and storage tank 32 were        added to the system.

Each of these stages of operation of the system of the invention willnow be described in greater detail. For convenience, the operation ofthe various valves and other components present in the refrigerant flowloop and which are used to control the flow of compressible refrigerantand non-freezing liquid during the operation of the system aresummarized in the tables presented in FIGS. 10A and 10B of the drawings.

In FIG. 3. the system is acting with the heat pump being in the normalair conditioning mode. Refrigerant flow is passing into the receiver 26.Because valve 24 is open, refrigerant passes to the expansion valve 12located within the building structure to provide a cooling effect, as ifthe TETU were not present in the system. In other words, except for thepresence of the TETU, the operation of the first and second heatexchangers is the same as previously described with respect to FIG. 1 ofthe drawings with the inside coil 9 acting as an evaporator coil and theoutside coil 4 acting as a condenser coil.

FIG. 4 depicts the operation of the system with the heat pump acting inthe normal heating mode as if the TETU 100 were not present in thesystem. In this mode, the expansion valve 12 is by-passed so that highpressure vapor passes through valves 13 and 31 to the receiver 26. Notethat the flow of refrigerant is exactly reversed from that describedwith respect to the normal air conditioning mode of FIG. 3. Valves 24and 29 are open, allowing flow through check valve 28 back to theexpansion valve 6 of the first heat exchanger of the heat pump system,as if the TETU were not present in the system.

FIG. 5 depicts the operation of the system with the heat pump being usedin a refrigeration mode in conjunction with the TETU to create coldstorage in the thermal energy storage tank 32. The refrigerant flowcomes out of the first heat exchanger of the heat pump with the coil 4of that exchanger acting in the condensing mode, the flow passingthrough valve 27 to the receiver 26. High pressure liquid passes throughvalve 23 to the expansion valve 22 to the auxiliary heat exchanger coil20. Freon is returned to the first heat exchanger of the heat pump withthe heat pump acting as if it were in the air conditioning mode.Meanwhile, the liquid pump 19 is circulating non-freezing liquid fromthe thermal energy storage tank 32 in heat exchange relationship withthe coil 20 of the auxiliary heat exchanger to cool the non-freezingliquid. Note that the second (inside) heat exchanger of the heat pump isnot active during this mode of operation.

FIG. 6 of the drawings depicts the operation of the system of theinvention in providing air conditioning to the inside of the buildingstructure, but without the compressor 1 and first heat exchanger of theheat pump running. This would be the normal operating mode of the systemduring peak air conditioning times of the day. Pump 19 is againcirculating non-freezing liquid from the thermal energy storage tank 32through one side of the auxiliary heat exchanger 20. Low pressure vaporfrom the refrigerant loop passes from inside the building structure tothe other side of the auxiliary heat exchanger 20 where it is condensedto the liquid state at low pressure. The low pressure liquid then passesto the Freon pump 18, through check valve 17, through solenoid valve 16and through check valve 15. Since check valve 31 is closed, highpressure liquid flows to the expansion valve 13 inside the structure andthrough coil 9 where it provides cooling to the inside air. Refrigerantis circulated back to the suction of the TETU and the cycle repeats. Theadvantage of operating the system in this manner is that, since thecompressor 1 is not being used, air conditioning can be provided to coolthe inside of the structure at a relatively low wattage.

FIG. 7 is a simplified schematic of a conventional heat pump, similar toFIGS. 1 and 2 which illustrates one problem which can occur with theoperation of a conventional heat pump, particularly during winter timeoperation. For example, assume the outside air temperature is 40° F. andthe system is operating in the heating mode shown in FIG. 2. In thismode of operation, the heat pump is, in effect, air conditioning theoutside air. If the coil 4 becomes too cold, it will literally freezeup. To keep this from happening, the unit is switched to the “defrostmode” shown in FIG. 7. In this mode, the system switches back to the airconditioning mode to thaw the outside coil 4. However, since the systemis now cooling the air inside the structure, it is generally necessaryto include an auxiliary heating element, such as the electric heatingelement 30 shown in FIG. 7 to heat the inside air which is beingdistributed inside the structure.

FIG. 8 shows an improved method of handling the thaw out cycle of theconventional heat pump system. In the operation of the system shown inFIG. 8, the system cools the thermal energy storage media (makes ice) inthe thermal energy storage tank 32 while the outside coil 4 is beingdefrosted. Note that since the second heat exchanger located inside thestructure is not being utilized, that no cold air is being distributedinside the structure. This solution eliminates the need to provideauxiliary electric heating elements inside the structure and saveselectricity.

Depending upon the ambient temperatures and other variables, the thermalenergy storage tank could eventually fill with ice. As a result, FIG. 9illustrates the identical system to FIG. 8, but with the addition of anauxiliary heating coil 33. Coil 33 can be used to heat the non-freezingliquid being circulated by the pump 19 back to the temperature it wasbefore the thawing cycle was started. Even though the system shown inFIG. 9 utilizes an auxiliary heating coil 33, it is still more efficientthan the conventional system shown in FIG. 7 because it is moreefficient to heat a liquid than to attempt to heat air. As an example, a3 ton air conditioning system requires about 11-12 Kwatts of electricityfor the operation of the heating coil 30 shown in FIG. 7. The same sizesystem requires only about 3 Kwatts of energy using the methodillustrated in FIG. 9.

An invention has been provided with several advantages. The thermalenergy transfer unit can be retrofitted to an existing Freon based heatexchanger without the requirement that the storage tank be located inclose proximity to the condensing unit or that the plumbing inside theassociated building structure be modified. The thermal energy transferunit can be retrofitted to several condensing units while sharing asingle remote thermal energy storage tank, also allowing the storagetank to use any of a variety of known thermal storage media for storingthermal energy. The thermal energy transfer unit is used to transferthermal energy from the existing condensing unit to the shared remotethermal energy storage tank during off-peak hours, while allowingrecovery of this energy from the common tank during peak hours.

The TETU uses a non-freezing liquid that never freezes in operation andtransfers heat to and from the common storage tank. The liquid iscirculated to and from the storage tank and the TETU by means of a pumpthat is located either at the tank or in the TETU. The TETU can includeone or several heat exchangers which transfer heat from the non-freezingliquid to the Freon being circulated by the condensing unit when storingenergy in the tank. The TETU uses this same heat exchanger, or others,to transfer the heat in the Freon to the non-freezing liquid (and thusto the tank) when air conditioning is performed without the condensingunit running. This heat transfer, without the use of the condensingunit, is accomplished by condensing the Freon to its liquid state andthen pumping the liquid Freon into the building to absorb heat where itvaporizes. After the Freon absorbs heat and vaporizes inside thestructure it returns to the heat exchanger(s) where it transfers itsheat to the non-freezing liquid and condenses to its liquid state. TheTETU also includes a pump means for pumping the liquid Freon when airconditioning is required without the condensing unit. The TETU allowsnormal air conditioning to be performed by the operation of thecondensing unit as if the TETU were not present. In this case, heat isneither being added nor extracted to the non-freezing liquid and thenon-freezing liquid pump is not running. The TETU is provided withappropriate valving and controls to accomplish these three functions.

While the invention has been shown in several of its forms, it is notthus limited but is susceptible to various changes and modificationswithout departing from the spirit thereof.

1. An improved method for heating and cooling a structure using a Freonbased heat pump system, comprising: a first refrigerant based heatexchanger capable of acting as either an evaporator or a condenser andadapted to absorb thermal energy from a structure in a cooling mode andsupply thermal energy to the structure in a heating mode; a secondrefrigerant based heat exchanger also capable of acting as either anevaporator or a condenser and adapted to absorb thermal energy fromambient atmosphere in a one mode and being adapted to transfer thermalenergy to ambient atmosphere in a different mode; a refrigerantdistribution loop containing a compressible Freon based refrigerant andconnecting the first and second heat exchangers in fluid flowcommunication; a refrigerant compressor adapted to cycle the refrigerantthrough the refrigerant distribution loop and the first and second heatexchangers; a reversing valve for converting the system from one of theaforesaid heating and cooling modes to the other of the modes byreversing the flow of Freon based refrigerant in the refrigerant flowloop; and wherein the improved method comprises the steps of: providinga thermal energy transfer unit in heat exchange relationship to therefrigerant distribution loop for applying energy conversion and storageto the Freon based heat pump system associated with the structure as theflow of Freon is reversed in the refrigerant flow loop during thecycling of the heating and cooling modes of operation of the system, thethermal energy transfer unit including a non-freezing liquid thermalstorage media located in a thermal storage tank.
 2. The method of claim1, further comprising the steps of: utilizing the thermal energytransfer unit to transfer heat from the thermal storage media in thethermal storage tank to the first heat exchanger of the Freon based heatpump system where it is rejected to outside air; transferring heat frominside air within the structure to the thermal storage media in thethermal storage tank without the compressor operating; and thereafter,allowing the first heat exchanger to transfer heat from the inside airof the structure to outside air in the same manner that such heattransfer was accomplished before the thermal energy transfer unit andthermal storage tank were added to the existing Freon based heat pumpsystem.
 3. The method of claim 2, wherein the first refrigerant basedheat exchanger includes an outside coil which acts as the evaporator inthe system when the system is in the heating mode for heating thestructure, and wherein the outside coil tends to ice up during theheating mode operation, normally requiring a thawing step between thecooling and heating modes of the system; and wherein the outside coil isthawed without the use of electric heating elements by reversing theflow of refrigerant in the refrigerant loop, thereby causing the outsidecoil to act as a condenser, the heat transfer between the refrigerantloop in the heat pump system and the storage media in the thermalstorage tank being used to cool the thermal storage media and make icein the thermal storage tank
 4. The method of claim 3, wherein thethermal storage tank has a fluid flow line and a fluid pump for pumpingnon-freezing liquid to and from the storage tank to the thermal energytransfer unit, and wherein the system includes an external heatingelement which is in heat exchange contact with the flow line to heat theliquid being circulated to the storage tank during the thawing step. 5.A method of air conditioning and heating a structure using a Freon basedheat pump system including a first refrigerant based heat exchangercapable of acting as either an evaporator or a condenser and adapted toabsorb thermal energy from a structure in a cooling mode and supplythermal energy to the structure in a heating mode, and also including asecond refrigerant based heat exchanger also capable of acting as eitheran evaporator or a condenser and adapted to absorb thermal energy fromambient atmosphere in a one mode and being adapted to transfer thermalenergy to ambient atmosphere in a different mode, the heat pump systemalso including a refrigerant distribution loop containing a compressibleFreon based refrigerant and including a compressor for cycling therefrigerant between a gaseous state and a liquid state, the improvementcomprising the steps of: locating a thermal energy transfer unit inproximity to the structure, for applying energy conversion and storageto the existing conventional Freon based heat pump, including the stepsof: locating a thermal storage tank remotely from the thermal energytransfer unit and connecting the storage tank to the thermal energytransfer unit by a fluid flow line; providing a pump for circulatingnon-freezing liquid in the fluid flow line to and from the storage tankfor transferring heat to and from the storage tank; wherein the thermalenergy transfer unit includes an auxiliary heat exchanger to transferheat from the non-freezing liquid to Freon being circulated within therefrigerant loop when storing energy in the tank and wherein the sameauxiliary heat exchanger is used to transfer the heat in the Freon tothe non freezing liquid, and thus to the tank, when air conditioning isperformed without the compressor running, the heat transfer without theuse of the compressor being accomplished by condensing the Freon to aliquid state and then pumping the liquid Freon into the structure toabsorb heat where it vaporizes, and wherein the Freon is then circulatedin heat exchange relationship with the auxiliary heat exchanger where ittransfers its heat to the non freezing liquid and condenses to itsliquid state after it absorbs heat and vaporizes inside the structure.6. The method of claim 5, wherein the thermal energy transfer unitallows normal air conditioning to be performed by the operation of thecondenser as if the thermal energy transfer unit were not present, inwhich case heat is neither being added to nor extracted from the nonfreezing liquid in the storage tank and the liquid pump in the fluidflow line is not running.
 7. The method of claim 6, wherein the thermalenergy storage tank uses a method for storing energy selected from thegroup consisting of: lowering the temperature of a liquid located withinan insulated tank; using an ice on pipe storage tank; using an ice ballstorage tank; and using an ice slurry method for storing thermal energy.8. A thermal energy transfer unit, comprising: at least one auxiliaryheat exchanger for transferring heat from a conventional heat pumpsystem having a mechanical compressor in a closed loop refrigerationcircuit to a non-freezing liquid medium that, in turn, transfers thatheat to or from at least one thermal storage tank; pump means forcirculating the non-freezing liquid medium; a valve control circuit forcontrolling the flow of the non-freezing liquid medium to theconventional heat pump system to enable the transfer of heat to thethermal storage tank without the mechanical compressor running.
 9. Thethermal energy transfer unit of claim 7, wherein the valve controlcircuit includes a series of valves which are used to start, stop andregulate the flow of heat from the conventional heat pump system to orfrom the thermal storage tank, the valve control circuit alsofunctioning to allow heat to be transferred by the heat pump system asif the thermal energy transfer unit and thermal storage tank were notpresent in the system.
 10. The thermal energy transfer unit of claim 9,further comprising: a plurality of thermal energy transfer units used inassociation with a plurality of heat pump systems to transfer heat to orfrom one or more shared thermal energy storage tanks.
 11. The thermalenergy transfer unit of claim 5, wherein the thermal energy transferoperates to duplicate the operation of a conventional air conditionercondensing unit while operating in the cooling mode, but without theconventional air conditioner condensing unit operating.